742 



GLOSSARY 



phytochromc a proteinaceous pigment isolated from plants whieh controls 

 a variety of responses to red and far-red light. 



pinocytosis the absorption of liquids by cells. 



pituitary an endocrine gland located on the floor of the brain in the sella 

 turcica. The pituitary secretes at least nine different hormones, some 

 of which stimulate other endocrine glands such as the thyroid, gonads, 

 etc. 



plasmodesmata minute cytoplasmic connections between cells. 



polymer a large molecule made up of repeating smaller units. 



polymerase an enzyme bringing about vmion of units into a polymer. 



procambium embryonic plant tissue which will mature into vascular tissue. 



prothoracic gland an endocrine gland of the insect which secretes ecdy- 

 sone, the growth and differentiation hormone. 



protista a group of the lowest unicellular forms of plants and animals. 



protochordate a simple animal which lacks a cranium and brain such as 

 the tunicates and shows similarities to the ancestors of the chordates. 



pseudopodia small protrusions of protoplasm from the main body of the cell. 



pupa the stage between the larva and imago in the development of an 

 insect. 



Qi„ Every temperature increase of 10° C. approximately doubles to triples 

 the speed of chemical and biological reactions. A temperature coeffi- 

 cient of a reaction may be expressed as the Qi„. 



rad a unit of absorbed radiation dose: i.e., 100 ergs/gram. 



rhizosphere the soil region in the immediate vicinity of the plant roots in 

 which the abundance or composition of the microbial population is 

 affected by the presence of the roots. 



RNA ribonucleic acid. 



R.Q. respiratory quotient. 



Schlieren peak the high point of a curve obtained with a special technique 

 of optical measurement. 



-SH-group sulfhydryl group. 



soma pertaining to the body; vegetative or non-reproductive portions. 



-SS-group a linkage formed between two compounds with -SH groups by 

 removal of hydrogen. 



stamen the flower organ that produces pollen. 



stele the central cylinder in the stems and roots of vascular plants. 



syngamy fusion of identical gametes. 



S:;„.„. the sedimentation constant corrected to conditions which would be 

 obtained in water at 20° C. 



T thymidine. 



TCA-cycle tricarboxylic acid (Krebs or citric acid) cycle. 



T-even phages the bacteriophages named T2, T4, T6. 



teratoma a tumor resulting from faulty embryonic differentiation and or- 

 ganization. 



THE tetrahydrocortisone, a Cortisol metabolite. 



therophytes annual plants in the life-form classification of Raunkaier. 



THF Tetrahydrocortisol, a Cortisol metabolite. 



